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Tokens in Python - Definition, Types, and More

Tokens in Python - Definition, Types, and More
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Whether you are a beginner who is eager to learn the basics or an experienced Python developer looking to expand your knowledge, this blog will provide you with a solid foundation for understanding tokens in Python. So, get ready to discover the building blocks of Python programming with tokens.

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What are Tokens in Python?

What are Tokens in Python?

In Python, when you write a code, the interpreter needs to understand what each part of your code does. Tokens are the smallest units of code that have a specific purpose or meaning. Each token, like a keyword, variable name, or number, has a role in telling the computer what to do.

For Example, let’s break down a simple Python code example into tokens:

# Example Python code
variable = 5 + 3
print("Result:", variable)

Now, let’s identify the tokens in this code:

  • Keywords (like β€˜if’ or β€˜while’ ) tell the computer about decision-making or loops.
  • Variable names (identifiers) are like labels for storing information.
  • Numbers and text (literals) represent actual values.
  • Operators (like + or –) are symbols that perform actions on values.

When the interpreter reads and processes these tokens, it can understand the instructions in your code and carry out the intended actions. The combination of different tokens creates meaningful instructions for the computer to execute.

Tokens are generated by the Python tokenizer, after reading the source code of a Python program. It breaks, the code into smaller parts. The tokenizer ignores whitespace and comments and returns a token sequence to the Python parser.

The Python parser then uses the tokens to construct a parse tree, showing the program’s structure. The parse tree is then used by the Python interpreter to execute the program.

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Types of Tokens in Python

Types of Tokens in Python

When working with the Python language, it is important to understand the different types of tokens that make up the language. Python has different types of tokens, including identifiers, literals, operators, keywords, delimiters, and whitespace. Each token type fulfills a specific function and plays an important role in the execution of a Python script.

1. Identifiers in Python

Identifiers is a user-defined name given to identify variables, functions, classes, modules, or any other user-defined object in Python. They are case-sensitive and can consist of letters, digits, and underscores. Yet, they cannot start with a digit. Python follows a naming convention called “snake_case,” where words are separated by underscores. Identifiers are used to make code more readable and maintainable by providing meaningful names to objects.

Examples of Python Identifiers

Examples of valid Python identifiers:

  • my_variable
  • my_function()
  • my_class
  • my_module
  • _my_private_variable
  • my_variable_with_underscores

Examples of invalid Python identifiers:

  • 1my_variable (starts with a number)
  • my-variable (contains a special character)
  • def (keyword)
  • MyVariable (different case from my_variable)

2. Keywords in Python

Keywords are reserved words in Python that have a special meaning and are used to define the syntax and structure of the language. These words cannot be used as identifiers for variables, functions, or other objects. Python has a set of 35 keywords, each serving a specific purpose in the language. 

There are 35 keywords in Python 3.11. They are:

andasassertasynccontinue
elseifnotwhiledef
exceptimportorwithdel
finallyinpassyieldelif
forisraiseawaitfalse
fromlambdareturnbreaknone
globalnonlocaltryclasstrue

3. Literals in Python

Literals are constant values that are directly specified in the source code of a program. They represent fixed values that do not change during the execution of the program. Python supports various types of literals, including string literals, numeric literals, boolean literals, and special literals such as None.

Literals in Python

Numeric literals can be integers, floats, or complex numbers. Integers are whole numbers without a fractional part, while floats are numbers with a decimal point. Complex numbers consist of a real part and an imaginary part, represented as “x + yj“, where “x” is the real part and “y” is the imaginary part.

String literals are sequences of characters enclosed in single quotes () or double quotes (“”). They can contain any printable characters, including letters, numbers, and special characters. Python also supports triple-quoted strings, which can span multiple lines and are often used for docstrings, multi-line comments, or multi-line strings.

Boolean literals represent the truth values “True” and “False“. They are used in logical expressions and control flow statements to make decisions based on certain conditions. Boolean literals are often the result of comparison or logical operations.

Special literals include None, which represents the absence of a value or the null value. It is often used to indicate that a variable has not been assigned a value yet or that a function does not return anything.

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4. Operations in Python

Operators are like little helpers in Python, using symbols or special characters to carry out tasks on one or more operands. Python is generous with its operators, offering a diverse set. These include the everyday arithmetic operators, those for assignments, comparison operators, logical operators, identity operators, membership operators, and even those for handling bits.

Type of OperatorDescriptionExample
Arithmetic OperatorsPerform mathematical operations such as addition, subtraction, multiplication, division, modulus, and exponentiation.+, -, *, /, %, **
Assignment OperatorsAssign values to variables, including the equal sign and compound assignment operators.=, +=, -=, *=, /=, %=
Comparison OperatorsCompare two values and return a boolean (True or False) based on the comparison.==, !=, >, <, >=, <=
Logical OperatorsCombine conditions and perform logical operations like AND, OR, and NOT.and, or, not
Identity OperatorsCompare the memory addresses of objects to check if they are the same or different.is, is not
Membership OperatorsTest if a value is present in a sequence (e.g., list, tuple, string).in, not in
Bitwise OperatorsPerform bit-level operations on binary numbers, allowing manipulation of individual bits.&

5. Delimiters in Python

Delimiters are characters or symbols used to separate or mark the boundaries of different elements in Python code. They are used to group statements, define function or class bodies, enclose string literals, and more. Python uses various delimiters, including parentheses β€˜()’, commas β€˜,’, brackets β€˜[]’, braces β€˜{}’, colons β€˜:’, and semicolons.

Punctuation MarkUsage
ParenthesesDefine function arguments, control the order of operations, and create tuples.
BracketsCreate lists, which are mutable sequences of values.
BracesDefine sets (unordered collections of unique elements) and dictionaries (key-value pairs).
CommasSeparate elements in tuples, lists, sets, and dictionaries. It is also used to separate function arguments and create multiple variable assignments.
ColonsDefine the body of control flow statements like if, else, for, while, and def.
SemicolonsSeparate multiple statements on a single line for brevity or to combine related statements.

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6. Whitespace and Indentation in Python

Whitespace and indentation play an important role in Python’s syntax and structure. Unlike many other programming languages, Python uses indentation to define blocks of code and determine the scope of statements. The use of consistent indentation is not only a matter of style but is required for the code to be valid and executable.

ConceptDescription
Standard IndentationIn Python, the standard indentation is four spaces.
Indentation MethodsIndentation can be done using spaces or tabs, but it’s recommended to use spaces for better compatibility and readability. Mixing tabs and spaces can lead to syntax errors.
Indentation in Control FlowIndentation is used to define the body of control flow statements like if, else, for, while, and def. The indented block of code following a colon (:) is executed when the control flow condition is met. The indentation level must be the same for all statements within the same block.
Whitespace and ReadabilityWhitespace, including spaces, tabs, and newlines, is used to separate tokens and enhance code readability. Excessive whitespace should be avoided, as it can hinder code comprehension. Python ignores whitespace within parentheses, brackets, and braces, allowing code formatting for improved readability.

Tokenizing in Python

Tokenizing is the process of breaking down a sequence of characters into smaller units called tokens. In Python, tokenizing is an important part of the lexical analysis process, which involves analyzing the source code to identify its components and their meanings. Python’s tokenizer, also known as the lexer, reads the source code character by character and groups them into tokens based on their meaning and context.

The tokenizer identifies different types of tokens, such as identifiers, literals, operators, keywords, delimiters, and whitespace. It uses a set of rules and patterns to identify and classify tokens. When the tokenizer finds a series of characters that look like a number, it makes a numeric literal token. Similarly, if the tokenizer encounters a sequence of characters that matches a keyword, it will create a keyword token.

Tokenizing is an important step in the compilation and interpretation process of Python code. It breaks down the source code into smaller components, making it easier for the interpreter or compiler to understand and process the code. By understanding how tokenizing works, you can gain a deeper insight into Python’s internal workings and improve your ability to debug and optimize your code.

How to Identify Tokens in Python Program

How to Identify Tokens in Python Program

There are two ways to identify tokens in a Python program:

  • Use the Python Tokenizer – The Python tokenizer is a built-in module that is useful for breaking down a Python program into its different elements. To use the tokenizer, you can import it. Then call the tokenize() function. This function will provide you with a series of tokens, each represented as a tuple. Within each tuple, you will find the type and its corresponding value.
  • Use a Regular Expression Library – Regular expressions are a tool for finding patterns in text. To use a regular expression library to identify tokens in a Python program. Start by creating an expression that matches the types of tokens you’re interested in. Once the regex is set up, you can apply it to your Python program to find and match the desired tokens.

Here is an example of how to use the Python tokenizer to identify tokens in a Python program:

import tokenize
import io
# Define your Python program as a string
python_code = "def my_function():\n  pass"
# Tokenize the Python program
tokens = tokenize.tokenize(io.BytesIO(python_code.encode('utf-8')).readline)
# Print the tokens
for token in tokens:
    print(token)

Output:

TokenInfo(type=63 (ENCODING), string=’utf-8′, start=(0, 0), end=(0, 0), line=”)
TokenInfo(type=1 (NAME), string=’def’, start=(1, 0), end=(1, 3), line=’def my_function():\n’)
TokenInfo(type=1 (NAME), string=’my_function’, start=(1, 4), end=(1, 15), line=’def my_function():\n’)
TokenInfo(type=54 (OP), string='(‘, start=(1, 15), end=(1, 16), line=’def my_function():\n’)
TokenInfo(type=54 (OP), string=’)’, start=(1, 16), end=(1, 17), line=’def my_function():\n’)
TokenInfo(type=54 (OP), string=’:’, start=(1, 17), end=(1, 18), line=’def my_function():\n’)
TokenInfo(type=4 (NEWLINE), string=’\n’, start=(1, 18), end=(1, 19), line=’def my_function():\n’)
TokenInfo(type=5 (INDENT), string=’  ‘, start=(2, 0), end=(2, 2), line=’  pass’)
TokenInfo(type=1 (NAME), string=’pass’, start=(2, 2), end=(2, 6), line=’  pass’)
TokenInfo(type=4 (NEWLINE), string=”, start=(2, 6), end=(2, 7), line=”)
TokenInfo(type=6 (DEDENT), string=”, start=(3, 0), end=(3, 0), line=”)
TokenInfo(type=0 (ENDMARKER), string=”, start=(3, 0), end=(3, 0), line=”)

Here is an example of how to use a regular expression library to identify tokens in a Python program:

import re
# Create a regular expression to match the different types of tokens
token_regex = r"(def|class|if|else|for|while|return|or|and|not|in|is|True|False|None|[+\-*/%=])|([a-zA-Z_]\w*)|(\"([^\"\\]|\\.)*\")|('([^'\\]|\\.)*')"
# Match the tokens in the Python program
tokens = re.findall(token_regex, "def my_function():\n  pass")
# Print the tokens
for token in tokens:
    print(token)

Output:

(‘def’, ”, ”, ”, ”, ”)
(”, ‘my_function’, ”, ”, ”, ”)
(”, ‘pass’, ”, ”, ”, ”)

The choice of identification method in Python programs depends on your requirements. If you need a more tough and accurate method, then you should use a regular expression library. If you need a simpler and more straightforward method, then you should use the Python tokenizer.

Token Libraries in Python

Token libraries are Python libraries that help developers to tokenize text. In Python, various token libraries are there that serve different purposes. Each has its strengths and weaknesses. Here’s a list of some popular token libraries in Python:

1. NLTK (Natural Language Toolkit):

  •  Comprehensive NLP library.
  •  Provides tools for word tokenization, sentence tokenization, and part-of-speech tagging.
  •  Suitable for general NLP tasks but may be resource-intensive for large datasets.

2. SpaCy:

  •   Known for speed and accuracy.
  • Offers a wide range of NLP features, including tokenization, part-of-speech tagging, named entity recognition, and dependency parsing.
  • Ideal for large datasets and tasks requiring speed and accuracy.

3. TextBlob:

  • Lightweight and user-friendly NLP library.
  • Includes tools for word tokenization, sentence tokenization, and part-of-speech tagging.
  • Suitable for small to medium-sized datasets, prioritizing simplicity.

4. Tokenize:

  • Simple and lightweight library for text tokenization.
  • Supports various tokenization schemes, including word tokenization, sentence tokenization, and punctuation removal.
  • Ideal for tasks emphasizing simplicity and speed.

5. RegexTokenizer:

  • Powerful tokenizer using regular expressions for text tokenization.
  • Allows custom tokenization schemes but may have a steeper learning curve.
  • Suitable for tasks requiring custom tokenization or prioritizing performance.

The choice depends on the programmers’ specific needs. For NLP beginners, NLTK or SpaCy is recommended for their comprehensiveness and user-friendly nature. SpaCy is preferable for large datasets and tasks requiring speed and accuracy. TextBlob is suitable for smaller datasets focusing on simplicity. If custom tokenization or performance is crucial, RegexTokenizer is recommended.

Conclusion

Tokens in Python serve as the fundamental units of code and hold significant importance for both developers and businesses. Proficiency in handling tokens is crucial for maintaining precise and efficient code and supporting businesses in creating dependable software solutions. In a continuously evolving Python landscape, mastering tokens becomes an invaluable asset for the future of software development and innovation. Embrace the realm of Python tokens to witness your projects flourish.

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Frequently Asked Questions (FAQ)

What is the role of tokens in Python programming?

Tokens in Python are the smallest units of a program, representing keywords, identifiers, operators, and literals. They are essential for the Python interpreter to understand and process code.

How are tokens used in Python?

Tokens are used to break down Python code into its constituent elements, making it easier for the interpreter to execute the code accurately.

Can you provide examples of Python keywords?

Certainly! Some common Python keywords include if, else, while, and for.

Why is tokenization important in Python?

Tokenization is crucial because it helps the Python interpreter understand the structure and syntax of code, ensuring it can be executed correctly.

What should I keep in mind when using tokens in my Python code?

When working with tokens, prioritize code readability, follow naming conventions, and be aware of potential token conflicts to write clean and efficient Python code.

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About the Author

Senior Consultant Analytics & Data Science

Presenting Sahil Mattoo, a Senior Consultant Analytics & Data Science at Eli Lilly and Company is an accomplished professional with 14 years of experience across data science, analytics, and technical leadership domains, demonstrates a remarkable ability to drive business insights. Sahil holds a Post Graduate Program in Business Analytics and Business Intelligence from Great Lakes Institute of Management.